The selection and arrangement of workpieces in bending presses, also called press brakes or bending machines, is typically accomplished to a high degree manually, and only partly assisted by the machine control. To this end, a bending plan is created which calculates the product-specific upper and lower tools and their theoretical position. However, there is no monitoring as to whether these tools are or were actually inserted into the machine. Furthermore, the tools can be introduced at positions which do not correspond to the process and comprise a potential hazard.
However, the exact position of the tools is required to perform high-quality bending sequences and to align the back stop fingers or a robot accordingly. A corresponding positioning is only possible by precise and work-intensive measurement by hand, and transfer to the machine control.
Inaccurate positionings, non-allowance in the bending plan or an incorrect number of tools can result in damage to machine and peripheral. This is also possible as a result of an incorrect choice of tool geometry. Furthermore, upper and lower tools with maximum loads are defined—here also incorrect handling can result in damage. Damage caused by incorrect insertions on press brakes and tools can additionally lead to demands of any kind with respect to the manufacturer. Apparatuses are already known which attempt to solve these problems, in part, but have a number of disadvantages. Thus, for example, a display device on the machine can merely predefine a desired position but not monitor and detect this.
Published patent application JP H09-052124A discloses a bending machine with upper and lower tool, a stop and a barcode reader which is disposed on the stop. Upper and lower tool are each provided with a barcode on their rear side which can be read out by the barcode reader. The barcode contains information about the condition of the tool. This information is transferred to an NC controller. In addition to the barcode reader, a contact sensor or end switch is provided on the stop by which of which the dimensions of the respective tool can be determined. Such a procedure is complex and time-consuming since the contact sensor must be moved several times and in different positions directly onto the tool.
With such a system, for example, tools on the outer sides of the machine cannot be detected since no (rear) stop can travel here as a result of the mechanism. In addition, only individually positioned tools can be detected. A plurality of tools pushed together (or arranged in a row) on a tool holder cannot be distinguished since the central tools cannot be detected by the known system as such. In particular, individually positioned tools can only be detected when the distances between the tools are sufficiently large in order that the rear stop or the fingers can travel in between. A barcode requires a relatively large amount of space, so that such a barcode cannot be shown on very small punches (upper tool) and dies (lower tool). In addition, the detection of the barcode on sloping surfaces of the tool is very liable to error so that not all tools can be reliably detected. Also, specially shaped tools cannot be detected if the rear stop cannot be moved mechanically between the tools. If the approximate position of the tool is not known before the detection process, there is a high risk of a collision with the rear stop. Since the workpieces to be processed also impact against the rear stop during positioning, the contact sensors are severely stressed and are easily damaged.
WO 2012/103565A1 discloses a method for equipping a bending press with a bending tool. Here a controlled handling device with a gripper is used for the bending tool. A control device generates control commands in order to move the tool from an actual position into a desired position when inserting into the tool holder. Only when the tool has reached the desired position, is it inserted in the tool holder and fixed there. The tools held by the handling device must be approached directly by the (rear) stop in order to determine their actual position. The method is complex and based on the basic principle that the tools inside the tool holder must adopt an exact position so that the desired bending plan can be carried out.
EP 0919300B1 discloses a bending machine in which the upper tools are provided with barcodes. A guide running in the Z direction for a scanner for reading the barcode is provided on the tool clamp for the upper tools on the side facing the operator. A linear scale, e.g. magnetic scale as position detection device is further provided on this tool clamp on the side facing the operator. The position data of the upper tools detected by the scanner are stored and made available again subsequently in a display. For producing the same product again, using the stored data the operator must place the tools precisely by hand according to the stored position. This bending machine is also based on the basic principle that the tools must adopt an exact position inside the tool holder so that the desired bending plan can be executed. However, the exact positioning and adjusting of the tool position requires high expenditure of time and personnel.
EP 1517761B1 relates to special tools and tool holders which can detect tool positions relatively imprecisely by means of sensors. In this case, it is not possible in some cases to classify tools qualitatively and geometrically. In addition, the high acquisition costs of the required peripherals, the maintenance intensity, the necessary new acquisition of special punches and dies and their restricted geometry are disadvantages. Furthermore, as a result of the sensors introduced into the machine and tool, limiting pressing forces are to be expected. In addition, movable sensors on upper and lower beams as well as necessary data and supply cables reduce the variability of a press brake. The number of possible bending parts is limited.
EP 1510267B1 discloses a method for displaying a tool arrangement in a press brake. On the basis of a displayed diagram it is determined whether the planned bending process is possible. Subsequently further tools are added for specific bending line sections and the process is repeated with the new arrangement. This process requires an exact positioning of the tools in the tool holder precisely as the previous method.
DE 3830488A1 discloses an electronic tool recognition system for press brakes. By means of this system it is possible with the aid of an electronic control to recognize the built-in tool geometry, to protect the tools against overloading and ensure the working safety for the operator.
DE 4442381A1 relates to an apparatus for position and shape recognition of upper beam tools on swivel bending machines and press brakes. Located behind the upper beam in a guide is a motor-displaceable slide on which a holder for a laser light curtain is mounted. With this the length of the built-in upper beam tools and their intermediate spaces are determined. The values are displayed numerically and graphically. In addition, a write-read head which reads out codes on the rear side of the upper beam tools is located in the holder.
All the known systems relate to the readout of codes and/or the detection of tool dimensions. The precise positioning of the tools inside the tool holder plays an essential role. In the prior art therefore it is necessary to position the tools exactly in relation to the tool holder, which brings with it the disadvantage of a complex and time-intensive equipping of the bending machine.